Sputum procalcitonin: a potential biomarker in stable bronchiectasis.

Sputum procalcitonin is elevated in exacerbations of bronchiectasis. The primary aim of this study was to investigate whether sputum procalcitonin levels are higher in patients with stable bronchiectasis than in healthy controls. We also assessed differences in procalcitonin levels in spontaneously expectorated and induced sputum samples and their repeatability 1 week later. Participants included were aged over 18 years and either had radiologically confirmed bronchiectasis or were healthy controls. Patients with bronchiectasis were clinically stable for at least 6 weeks and had spontaneous and induced sputum collected at visit 1 and again 7 days later. Only induced sputum samples were collected from healthy controls during visit 1. Sputum procalcitonin concentrations in sputum were measured. In total, 30 patients with bronchiectasis and 15 healthy controls were enrolled in this observational study. In the pooled data from visit 1 and 2, the geometric mean procalcitonin level in induced sputum was significantly higher in the bronchiectasis group than in the healthy control group (1.5 ng·mL-1, 95% CI 1.0-2.1 ng·mL-1 versus 0.4 ng·mL-1, 95% CI 0.2-0.9 ng·mL-1; mean ratio 3.6, 95% CI 1.5-8.6; p=0.006). Mean procalcitonin level was higher in spontaneous sputum than in induced sputum at visit 1 (1.8 ng·mL-1, 95% CI 1.2-2.7 ng·mL-1 versus 1.1 ng·mL-1, 95% CI 0.7-1.8 ng·mL-1) and visit 2 (1.5 ng·mL-1, 95% CI 1.0-2.5 ng·mL-1 versus 1.2 ng·mL-1, 95% CI 0.8-1.6 ng·mL-1; p=0.001). Repeating spontaneous and induced sputum procalcitonin levels 1 week later produced similar concentrations (p=0.29, intraclass correlation coefficient (ICC)=0.76 and p=0.72, ICC=0.70, respectively). Sputum procalcitonin is increased in patients with stable bronchiectasis and has potential as a biomarker of airway inflammation and infection in bronchiectasis.

SARS-CoV-2 viral load dynamics and real-time RT-PCR cycle threshold interpretation in symptomatic non-hospitalised individuals in New Zealand: a multicentre cross sectional observational study.

We conducted a multicentre cross sectional observational study of laboratory, public health and hospitalisation data for PCR-confirmed COVID-19 cases within the New Zealand Northern Region, between 12 February and 8 June 2020. The aim of this study was to describe population level SARS-CoV-2 upper respiratory tract (URT) viral load dynamics by stratifying positivity rates and polymerase chain reaction (PCR) cycle threshold (Ct) values of URT samples from COVID-19 cases by days since symptom onset, and to explore utility of Ct values in determining length of time post-infection and thus potential infectivity. Of 123,124 samples tested for SARS-CoV-2 by PCR, 579 samples (407 positive and 172 negative) from 368 symptomatic non-hospitalised individuals with PCR-confirmed infection were included. Sample positivity rate was 61.5% (8/13) for pre-symptomatic samples, rising to 93.2% (317/340) for samples collected during the purported symptomatic infectious period (days 0-10 post-symptom onset), and dropping to 36.3% (82/226) for post-infectious period samples (day 11 onwards). URT viral load peaked shortly after symptom onset, with median Ct values ranging 20.00-29.99 until 15 days post-symptom onset, and >30.00 after this time. Of samples with a Ct value of <20.00, 96.1% were collected during the symptomatic infectious period. However, of samples with a Ct value ≥30.00 and ≥35.00, 46.9% and 18.5%, respectively, were also collected during the symptomatic infectious period. The findings of this study indicate that at or soon after symptom onset represents the optimum time to test for SARS-CoV-2 in the URT, with median Ct values suggesting the useful testing window extends until around 15 days post-symptom onset. In asymptomatic individuals or those with unknown dates of symptom onset, Ct values <20.00 imply recent onset/potential infectivity, but Ct values ≥30.00 or ≥35.00 do not exclude recent onset/potential infectivity. Individual sample Ct values should not be used as an absolute marker of length of time post-infection or to exclude infectivity where date of symptom onset is unavailable.

Isolate independent molecular typing improves the yield of O typing of infections due to Shiga toxin producing Escherichia coli.

Molecular screening has increased detection of Shiga-toxin producing Escherichia coli (STEC). However, it is difficult to isolate the organism for epidemiological typing. We applied a molecular method for direct detection of nine O types from 110 stx positive faeces samples and compared the results with conventional isolate based methods. Using conventional methods 55/110 (50%) samples were O typed. Using the molecular method, 72/110 (65%) were O typed, including 23/38 (61%) culture negative samples. Combining both techniques typed 88/110 (80%) of samples. Molecular typing increased detection of O128 (2-25%, p<0.001), O26 (11-16%) O45 (0-6%) and O103 (1-6%) infections. Molecular typing of STEC direct from faecal samples improved O type yield; risk of bias in epidemiological and surveillance activities may be reduced by inclusion of culture independent typing methods.